Thin-film transistors (TFTs) based upon various organic and inorganic (e.g., metal oxide) semiconductors have been developed. To ensure good device performance, compatible materials for the layers (e.g., the gate dielectric layer, the passivation layer, and the etch-stop layer) adjacent to the semiconductor component are equally critical. While the function of these layers requires materials having different properties, it is generally desirable that these materials can be directly photopatterned without the use of a photoresist to simplify the overall manufacturing process, and in particular, to reduce the number of photolithography steps.
Most state-of-the-art photopatternable materials are based upon photocurable polymers and/or photopolymerizable compounds incorporating photosensitive moieties such as carbon-carbon double bonds, epoxides, Novolak/diazoquinones, or photogenerated acid groups. Often, these systems require one or more photoinitiators, photosensitizers, and/or photoacid generators to carry out the photochemical reactions efficiently. The presence of the photoinitiators, photosensitizers, or photoacid generators usually is not a concern if these photopatternable materials are used as photoresists, in which case, they are stripped off after the patterning step and are not incorporated as part of the final device. However, these systems will not be good material candidates as gate dielectrics (or other layers adjacent to the semiconductor layer) in a transistor device, because the photoinitiators, photosensitizers, or photoacid generators tend to promote interfacial charge trapping which can lead to deteriorated transistor characteristics such as threshold voltage shift, hysteresis, and increased current leakage.
Accordingly, there is a need in the art for photopatternable compositions that can be used to provide photopatterned dielectrics that are substantially free of any photoinitiators, photosensitizers, or photoacid generators, but at the same time can be solution-processed and cured efficiently.